Most carburetors on small internal combustion engines control engine speed with a throttle valve. The valve is mounted to a throttle shaft. Carburetors using a throttle valve (butterfly valve) have a throttle shaft that is assembled into a bore which is machined transversely to the throttle bore of the carburetor. The valve is attached to the shaft so that it aligns with the throttle bore. As the shaft rotates the valve opens the throttle bore passage, allowing air to flow through the bore to the engine.
In conventional carburetors C, the throttle shafts TS are retained by using a single e-ring ER, positioned at the opposite side of the throttle shaft TS from the throttle return spring RS (FIGS. 1 and 2). Due to having only one retainer, the throttle shaft TS is allowed to move in the direction of the e-ring ER due to an axial force F1, which causes the throttle return spring RS to compress and tends to cause the throttle valve TV to collide with the side of the throttle bore TB (FIG. 3). Axial movement in the opposite direction due to an axial force applied by F2 is stopped by the e-ring ER.
Attempts to fix this problem have included installing collars on both ends of the throttle shaft. This solution tends to be costly to assemble and to manufacture.
It is desirable to provide an improved throttle retainer assembly that reduces or eliminates the drawbacks associate with conventional throttle shaft retainer systems and methods.